cmd/tail/read.c

/*
 * Copyright (c) 1991, 1993
 *  The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Edward Sze-Tyan Wang.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/types.h>
#include <sys/stat.h>

#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <strings.h>
#include <unistd.h>

#include "extern.h"

/*
 * bytes -- read bytes to an offset from the end and display.
 *
 * This is the function that reads to a byte offset from the end of the input,
 * storing the data in a wrap-around buffer which is then displayed.  If the
 * rflag is set, the data is displayed in lines in reverse order, and this
 * routine has the usual nastiness of trying to find the newlines.  Otherwise,
 * it is displayed from the character closest to the beginning of the input to
 * the end.
 */
int
bytes(FILE *fp, const char *fn, off_t off)
{
    int ch, len, tlen;
    char *ep, *p, *t;
    int wrap;
    char *sp;

    if ((sp = p = malloc(off)) == NULL)
        err(1, "malloc");

    for (wrap = 0, ep = p + off; (ch = getc(fp)) != EOF; ) {
        *p = ch;
        if (++p == ep) {
            wrap = 1;
            p = sp;
        }
    }
    if (ferror(fp)) {
        ierr(fn);
        free(sp);
        return (1);
    }

    if (rflag) {
        for (t = p - 1, len = 0; t >= sp; --t, ++len)
            if (*t == '\n' && len) {
                WR(t + 1, len);
                len = 0;
        }
        if (wrap) {
            tlen = len;
            for (t = ep - 1, len = 0; t >= p; --t, ++len)
                if (*t == '\n') {
                    if (len) {
                        WR(t + 1, len);
                        len = 0;
                    }
                    if (tlen) {
                        WR(sp, tlen);
                        tlen = 0;
                    }
                }
            if (len)
                WR(t + 1, len);
            if (tlen)
                WR(sp, tlen);
        }
    } else {
        if (wrap && (len = ep - p))
            WR(p, len);
        len = p - sp;
        if (len)
            WR(sp, len);
    }

    free(sp);
    return (0);
}

/*
 * lines -- read lines to an offset from the end and display.
 *
 * This is the function that reads to a line offset from the end of the input,
 * storing the data in an array of buffers which is then displayed.  If the
 * rflag is set, the data is displayed in lines in reverse order, and this
 * routine has the usual nastiness of trying to find the newlines.  Otherwise,
 * it is displayed from the line closest to the beginning of the input to
 * the end.
 */
int
lines(FILE *fp, const char *fn, off_t off)
{
    struct {
        int blen;
        uint_t len;
        char *l;
    } *llines;
    int ch, rc;
    char *p, *sp;
    int blen, cnt, recno, wrap;

    if ((llines = malloc(off * sizeof (*llines))) == NULL)
        err(1, "malloc");
    bzero(llines, off * sizeof (*llines));
    p = sp = NULL;
    blen = cnt = recno = wrap = 0;
    rc = 0;

    while ((ch = getc(fp)) != EOF) {
        if (++cnt > blen) {
            if ((sp = realloc(sp, blen += 1024)) == NULL)
                err(1, "realloc");
            p = sp + cnt - 1;
        }
        *p++ = ch;
        if (ch == '\n') {
            if ((int)llines[recno].blen < cnt) {
                llines[recno].blen = cnt + 256;
                if ((llines[recno].l = realloc(llines[recno].l,
                    llines[recno].blen)) == NULL)
                    err(1, "realloc");
            }
            bcopy(sp, llines[recno].l, llines[recno].len = cnt);
            cnt = 0;
            p = sp;
            if (++recno == off) {
                wrap = 1;
                recno = 0;
            }
        }
    }
    if (ferror(fp)) {
        ierr(fn);
        rc = 1;
        goto done;
    }
    if (cnt) {
        llines[recno].l = sp;
        sp = NULL;
        llines[recno].len = cnt;
        if (++recno == off) {
            wrap = 1;
            recno = 0;
        }
    }

    if (rflag) {
        for (cnt = recno - 1; cnt >= 0; --cnt)
            WR(llines[cnt].l, llines[cnt].len);
        if (wrap)
            for (cnt = off - 1; cnt >= recno; --cnt)
                WR(llines[cnt].l, llines[cnt].len);
    } else {
        if (wrap)
            for (cnt = recno; cnt < off; ++cnt)
                WR(llines[cnt].l, llines[cnt].len);
        for (cnt = 0; cnt < recno; ++cnt)
            WR(llines[cnt].l, llines[cnt].len);
    }
done:
    for (cnt = 0; cnt < off; cnt++)
        free(llines[cnt].l);
    free(sp);
    free(llines);
    return (rc);
}